search with pagination is not working in laravel

I make it in 1 route with in route

Route::get('/all-students', 'AdminController@studentList')->name('admin.student');
Route::post('/all-students', 'AdminController@searchByClassRoll')->name('search-by-class-roll');

in controller funtion student list

public function studentList(Request $request)
{
    Session::put('url.intended2', URL::current());
    Session::put('url.intended', URL::previous());

    if (isset($request->class)) {
        if (isset($request->roll)) {
            if ($request->class == 'all') {
                $students = DB::table('students')
                    ->where('roll', '=', $request->roll)
                    ->orderBy('id', 'DESC')
                    ->paginate(20);
            } else {
                $students = DB::table('students')
                    ->where('roll', '=', $request->roll)
                    ->where('class', '=', $request->class)
                    ->orderBy('id', 'DESC')
                    ->paginate(20);
            }
        } else {
            if ($request->class == 'all') {
                return redirect()->route('admin.student');
            } else {
                $students = DB::table('students')
                    ->where('class', '=', $request->class)
                    ->orderBy('id', 'DESC')
                    ->paginate(20);
            }
        }
    } else {
        $students = DB::table('students')
            ->orderBy('id', 'DESC')
            ->paginate(20);
    }


    return view('admin.student-list')->with('students', $students);
}

post method

public function searchByClassRoll(Request $request)
{
    $class = $request->class;
    $roll = $request->roll;
    if (isset($request->class)) {
        if (isset($request->roll)) {
            return redirect()->route('admin.student', ['class' => $class, 'roll' => $roll]);
        } else {
            return redirect()->route('admin.student', ['class' => $class]);
        }
    }
}

in blade

@if(method_exists($students,'links'))
    {!! $students->links() !!}
@endif

normally when I click page 2 it returns all-students?page=2 when I search something all-students?class=2 and then i click on pagination page it returns again all-students?page=2 and remove the search data from URL.

form from view

<form action="{{ route('search-by-class-roll') }}" method="post">
    {{ csrf_field() }}
    <input type="hidden" name="type" value="student_list">
    <div class="row gutters-8">
        <div class="col-4-xxxl col-xl-4 col-lg-3 col-12 form-group">
            <div class="ui-alart-box">
                <div class="default-alart">
                    <div class="result" role="alert">
                        @if(app('request')->input('class') || app('request')->input('roll'))
                            <a href="{{route('admin.student')}}">See All</a><span> | </span>
                        @endif
                        Showing results {{$students->count()}} of {{$students->total()}} entries
                    </div>
                </div>
            </div>
        </div>
        <div class="col-3-xxxl col-xl-3 col-lg-3 col-12 form-group">
            <input type="number" name="roll" placeholder="Search by Roll..." class="form-control">
        </div>
        <div class="col-4-xxxl col-xl-3 col-lg-3 col-12 form-group">
            <select class="select2 form-control" name="class" required>
                <option value="all">All Classes</option>
                <option value="baby">baby</option>
                <option value="nursery">nursery</option>
                <option value="1">one</option>
                <option value="2">two</option>
                <option value="3">three</option>
                <option value="4">four</option>
                <option value="5">five</option>
                <option value="6">six</option>
                <option value="7">seven</option>
                <option value="8">eight</option>
                <option value="9">nine</option>
                <option value="10">ten</option>
            </select>
        </div>
        <div class="col-1-xxxl col-xl-2 col-lg-3 col-12 form-group">
            <button type="submit" class="fw-btn-fill btn-gradient-yellow">SEARCH</button>
        </div>
    </div>
</form>

i want to made this because I want this in 1 URL just because if someone manually entered the URL with search data he can see the output. but in here I can't get the result with pagination from blade. when I turned into page 2 it remove the search variable from URL. and paginate the whole data. how can I get result with pagination after search?

Coming directly to your controller. You don't need any other route or method you can handle this filtering on same route and in same method.

public function studentList(Request $request)
{
    if(!empty($request)){
        $query = $request->all();
       $students = DB::table('students')->orderBy('id', 'DESC');
       if(isset($request->class) AND $request->class != '' AND $request->class != 'all')
           $students = $students->where('class', '=', $request->class);
       if(isset($request->roll) AND $request->roll != '')
           $students = $students->where('roll', '=', $request->roll);
       $students = $students->paginate(20);

        return view('admin.student-list', compact('students','query'));
    }

    $students = DB::table('students')
                ->orderBy('id', 'DESC')
                ->paginate(20);
   return view('admin.student-list', compact('students'));
}

Change few things in your view

<form action="{{ route('admin.student') }}" method="get"> change route and method to get
{{ csrf_field() }} //remove this

Below your table inside view write this code. The appends() is most important otherwise pagination in your filtered data won't work.

@if(isset($query))
  {{ $students->appends($query)->links() }}
@else
  {{ $students->links() }}
@endif